This seems to have started happening within the past month, and it's a little annoying during development.

Here's what happens: you make some changes, hit Ctrl+F5, and javascript doesn't work properly on your site. You look at the console in browser's dev tools, and see errors like "Uncaught ReferenceError: jQuery is not defined". In the view source, you notice that jquery.js is being included after scripts that have declared a dependency on jquery.js. For example, in one of my pages where I'm having this issue, I'm using these Script includes in my .cshtml:

Script.Require("jQuery");
Script.Require("jQueryUI_Button");
Script.Require("jQueryUI_Tabs");
Script.Require("jQueryUI_Slider");
Script.Require("jQueryUI_Dialog");
Script.Require("jQueryUI_Slider");

, and the jQueryUI_... resources have declared deps on jQuery. But they are included before jquery in the html.

Usually after one or more cycles of killing Cassini, cleaning the solution, rebuilding, and launching via Ctrl+F5 again, the problem goes away for a while. We mentioned this during this week's orchard weekly meeting and at least one or two other people mentioned they too were having this problem.